while-loop.cpp

#include <iostream>
using namespace std;

int main() {

    // ===================================================
    // 1. BASIC WHILE LOOP
    // ===================================================
    // Loops through a block of code as long as condition is true
    cout << "=== 1. BASIC WHILE LOOP ===" << endl;
    
    int i = 0;
    while (i < 5) { // Condition: run while i is less than 5
        cout << i << "\n";
        i++; // Increment variable, crucial to avoid infinite loops!
    }


    // ===================================================
    // 2. WHILE LOOP - COUNTDOWN EXAMPLE
    // ===================================================
    cout << "\n=== 2. COUNTDOWN EXAMPLE ===" << endl;

    int countdown = 3;
    while (countdown > 0) { // Condition: run while countdown > 0
        cout << countdown << "\n";
        countdown--; // Decrement counter
    }
    cout << "Happy New Year!!\n";


    // ===================================================
    // 3. WHILE LOOP - STEP BY EVEN NUMBERS
    // ===================================================
    cout << "\n=== 3. EVEN NUMBERS (0 TO 10) ===" << endl;

    int evenCounter = 0;
    while (evenCounter <= 10) {
        cout << evenCounter << "\n";
        evenCounter += 2; // Increment by 2 instead of 1
    }


    // ===================================================
    // 4. DO/WHILE LOOP (BASIC)
    // ===================================================
    // Executes code block ONCE before checking if condition is true
    cout << "\n=== 4. BASIC DO/WHILE LOOP ===" << endl;

    int j = 0;
    do {
        cout << j << "\n";
        j++;
    } while (j < 5); // Note: Semicolon ';' is required after condition!


    // ===================================================
    // 5. DO/WHILE - CONDITION FALSE FROM THE START
    // ===================================================
    // Demonstrates that do/while ALWAYS runs at least once
    cout << "\n=== 5. DO/WHILE (FALSE CONDITION) ===" << endl;

    int k = 10;
    do {
        // Runs even though (10 < 5) is false!
        cout << "k is " << k << "\n"; 
        k++;
    } while (k < 5);


    // ===================================================
    // 6. PRACTICAL EXAMPLE: REVERSE NUMBERS
    // ===================================================
    cout << "\n=== 6. REVERSE NUMBERS ===" << endl;

    int numbers = 12345;
    int revNumbers = 0;

    // Loop continues as long as 'numbers' is not 0 (non-zero is true)
    while (numbers) {
        // Get last digit and append to reversed number
        revNumbers = revNumbers * 10 + numbers % 10; 
        // Remove the last digit
        numbers /= 10; 
    }
    cout << "Reversed numbers: " << revNumbers << "\n";


    // ===================================================
    // 7. PRACTICAL EXAMPLE: WHILE LOOP WITH IF-ELSE
    // ===================================================
    cout << "\n=== 7. WHILE WITH IF-ELSE (YATZY GAME) ===" << endl;

    int dice = 1;
    while (dice <= 6) {
        if (dice < 6) {
            cout << "No Yatzy\n";
        } else {
            cout << "Yatzy!\n";
        }
        dice += 1;
    }

    return 0;
}